NONCIRCULAR WIGNER-SEITZ CELLS IN STRONGLY SEGREGATED BLOCK-COPOLYMERS

A perturbation method is developed that allows for the systematic calculation of the elastic free energy of block copolymer microphases and goes beyond the approximation of a circularly (or spherically) symmetric Wigner-Seitz cell. The method is applicable in the limit of strong segregation between dissimilar blocks and to any type of microphase or copolymer architecture. As a demonstration of its utility, I perform an explicit calculation of the elastic free energy for the hexagonal microphase of diblock copolymers. In the composition window where this microphase is observed, I show that the circular cell approximation of Semenov underestimates the elastic energy of the corona by no more than 6%.